Reversible unidirectional antenna



Dec. 1, 1942. p, s CARTER 7 2,303,610

REVERSIBLE UNIDIRECTIONAL ANTENNA Filed May 16, 1941 ANTENNA To TRANSMITTER INV EN TOR.

' PHI IP CARTER ATTORNEY.

Patented Dec. 1, 1942 k REVERSTBLE UNIDIRECTIONAL ANTENNA Philip '8. Carter, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application May 16, 1941, Serial No. 393,699

7 Claims.

The present invention relates to traveling wave antennae and, more particularly, to such antennae which are designed to be unidirectional in either of two desired opposite directions.

An object of the present invention is the elimination of termination losses in reversible traveling wave antennae.

Another object of the present invention is to provide a reversible traveling wave antenna which does not waste power through the use of terminating resistors.

Still another object is to provide an elongated traveling wave antenna in which energy arriving at the end remote from the input end is reapplied to the input and reradiated and which antenna may have the direction of radiation reversed if desired.

The present invention contemplates the coupling, through impedance matching networks, if necessary, of a transmission line to each end of a traveling wave antenna. Then to this trans' mission line at a predetermined point isconnected another transmission line by means of which the antenna is energized or by means of which the antenna is connected to a receiving apparatus. The first-mentioned transmission line has connected thereto at each side of the connection of the second transmission line switches by means of which shunt reactances may be selectively connected thereto in such location that energy from the transmitter is applied to one end of the traveling wave antenna and the major portion of the energy is radiated throughout, the length of the antenna. Such energy as is not radiated by the time the traveling wave reaches the other end of the antenna is picked up by the transmission line and reapplied to the originating end in a proper amplitude and phase relationship with respect to the energy therein to be in an additive relationship thereto. The shunt reactances are arranged to be selectively switched into and out of circuit with the transmission line in order'that the antenna may be made unidirectional in either of two opposite directions along the axes of the antenna.

Further objects and features of the present invention will be more fully understood from the following detailed description, which isa'ccompanied by a drawing in which Figure 1 illustrates the application of the principles of the present invention to a rhombic antenna and Figure 2 illustrates the application to a generalized traveling wave antenna.

Referring, now, to Figure 1, IO and 20 denote a pair of conductors disposed in a generally rhombic configuration on a horizontal plane. At end ll of the antenna is connected a short sectionof transmission line l2, while at the other end l3 of the traveling wave antenna is connected another transmission line H which is ergy is directly applied to end directly connected to the transmission line section l2. At substantially the midpoint of the transmission line section I2 is connected a second transmission line TE by means of which the antenna is energized from a transmitter (not shown). At each side of the point of connection of-transmission line TL to transmission line section l2, at a distance therefrom of a quarter wavelength, are connected 'shunt reactances I5 and H3. The reactances are so related to the total conductor lengththrough the antenna and transmission lines I4 and I2 that the energy reapplied to the feed end of the antenna is in phase with energy originally applied. The shunt reactances I 5 and I6 are arranged to be selectively connected and disconnected from transmission line section l2 by'means of switches A and B. By switching in either shunt and disconnecting the other the antenna may be made unidirectional in its characteristics in either of two desired opposite directions. For example, if it is desired to radiate energy in the direction indicated by arrow E, switch A is closed and switch B is open. Under these circumstances energy arriving along transmission line TL from the transmitter is applied to the traveling wave antenna at end I I and progresses along the traveling Wave antenna in'the direction of arrow F. As it travels along the antenna a large portion of the energy is radiated and that which arrives at end I3 is applied to transmission line 14 and thus conducted back to end H, where it again enters the antenna'and has a second opportunity of radiation. The shunt reactance l5, together with the M4 line section l2, transforms the voltage of the energy arriving along transmission line I 4 to such value that it combines directly with energy arriving at end ll directly from the transmitter by way of transmission line TL. The shunt reactance l5, together with the M4 line section I2, acts as a transformer, having such proportions that the voltage is stepped up in a ratio of F to 1, where 11L is the total attenuation over theantenna and return line, in proceeding from the feedback line H to the input end of the antenna and the energy arriving by way of transmission line H! is in phase with the energy arriving by way of transmission line TL. If it is desired to transmit energy in the direction indicated by arrow W, switch A is open and switch B closed. In this case en- I3 of the traveling wave antenna and travels through the antenna in the direction indicated by arrow W. That which arrives at end II is transformed by shunt reactance-l6 to proper voltage value to combine directly with'energ arriving from the transmitter by way of transmission line TL.

It will thus be seen that I have perfected a traveling wave antenna which may be made seleclength and position of shunt frequency of said antenna, and means for energizing said antenna connected to said transmission line midway between said points of connection.

3. In combination, a traveling wave antenna having a pair of ends, a transmission line connecting said ends, a pair of shunt reactances detail in my prior copending application, Serial I #358,059, filed September 24, 1940, (RCA D. #19285), to which reference "maybe rhade for a more complete disclosure'thereo'fu it is believed sufiicient for the present case to merely indicate that reactances l and I6 are so located and of such length as to transform the voltage arriving from the far end of the antenna to such value that it may be reapplied to theinput end of the antenna. a 1 V 7 In Figure 2 I have shown a modification of my invention as applied to any antenna of the trav-.

cling wave type. The antenna is indicatedgenerally by a box 21. Since the impedance of the antenna may not in all cases be thesame as the impedance of the transmission line Hi, impedance matching shunt circuits 22-and-23 may be connected at each end of the antenna. These shunt circuits must be included in case the impedance of the antenna is substantially diiferent from that of the feeder lines, sincein such case reflection would otherwise 'occur at each end of the antenna and a pure traveling wave would not therefore be obtained. I haveheretofore more iully described the theory of operation of the impedance matching shunts such cated by reference characters 22 and 23 in my prior Patents #1,909,610, granted May l6,-. 1933, and #2,109,801, granted November 5, 19 35, to which patents reference may be made for a more complete description. However, for present purposes, itis believed sufiicient to know that they. match the impedance of the antenna and transmission line connected theretowhereby reflection is prevented. The direction of radiation of antenna 2| of Figure 2.may be reversed in the same way as described above with reference to the rhombic antenna shown in Figure 1. That is, by closing switch B the antenna will radiate in the direction W and by closing switch A the antenna will radiate in the direction E. a

While I have particularly shown and described several modifications of my invention, I wish it to be clearly understood that my invention is notlimited thereto but that modifications and imas those indi-v provements within the scope of the invention may be made.

I claim: I I

1. In combination, a traveling wave antenna having a pair of ends, a transmission line connecting said ends, a pair of shunt reactances arranged to be selectively connected to said transmission line adjacent one of said ends, the points of connection of said reactances being spaced along said transmission line a predetermined distance, and means for energizing said antenna connected to said transmission linemidway between said points of connection. 1

2. In combination, a traveling waveantenna having a pair of ends, a transmission line connecting said ends, a pair of shunt reactances arranged to be selectively connected to said trans-.

mission line adjacent one of said ends, the points of connection of said reactances being spaced along said transmission line a distance equal to a half wavelength-to the operating arrangedto beselectively connected to said transmission line adjacent one of said ends, the points of connection of said reactances being spaced along said transmission line a distance equal to a half wavelength to the operating frequency of said antenna, and a second transmission line connecting said antenna to a high frequency transducer connected to said first transmission line midway between the points of connection of said shunt reactances.

4. In combination, a traveling wave antenna having a pair of separated ends, a transmission line connecting said ends, means for energizing said antenna connected to saidtransmissi-on line at a predetermined distance from its connection to one of said ends, and a pair of shunt reactances arranged to be selectively connected to said transmission line whereby the direction of radiation from said antenna may be reversed, one of said reactances being disposed at the junction of said transmission line and the separately mentioned one of said ends and the other at said predetermined distance from the connection of said energizing means to said transmission line.

5. In combination, a traveling wave antenna having a pair of ends, a transmission line connecting saidv ends, means for energizing said an-.

tenna connected to said transmission line at a distance equal to one-quarter of the operating wavelength from its connection to one of said ends and a pair of shunt reactances arranged to be selectively connected to said transmission line whereby the direction of radiation from said antenna may be reversed, one of said reactances being disposed atthe junction of said transmission line and the separately mentioned one of said ends and the other at a distance equal to one-quarter of the operating wavelength from the connection of said energizing means to said transmission line.

6. A rhomb-ic antenna comprising a pair of conductors having their ends adjacent and their midpoints separated, a transmission line connecting one ,pair of adjacent ends to the other pair of adjacent ends, a pair of shunt reactances arranged to beselectively connected to said transmission line adjacent one pair of adjacent ends, the point of connection of said reactances being spaced along said transmission line a distance equal to one-half the operating wavelength, and means for energizing said antenna connected to said transmission line between said points of connection of said reactances.

7. A rhombic' antenna comprising a pair of conductors having. their ends adjacent and their midpoints separated, a transmission line connecting one pair of adjacent ends to the other pair of adjacent ends, acpair of-shunt reactances arrangedto be selectively connected to said transmission line adjacent one pair ofadjacent ends, the points of connection of said reactances being spaced along said transmission line, and means for energizing said antenna connected to said transmission line between said points of connection of said reactances.

. PHILIP S. CARTER. 

